This invention relates to labelling of high-voltage fuses. The labelling of low voltage fuses, i.e. fuses having a voltage rating up to 600 volts does not present any particular difficulties and this is also true in regard to fuses having a voltage rating up to a few kv. The length of fuse tubes increases as the rated voltage of fuses increases and under such conditions the temperature rise of fuse tubes may be so high as to call for heat resistant labelling means for providing fuse tubes with the required information as to the origin of the product, its rating, etc.
Low voltage fuses are relatively short and there is an intense axial heat flow in such fuses. As a result of this fact, the temperature distribution along the fuse tube of a low voltage fuse is substantially in the shape of a parabola having its peak in the transverse median plane of the fuse and its lowest value adjacent the terminals of the fuse. Because of the intense axial heat flow the highest temperatures at the outside of the fuse tube are moderate. This makes it readily possible to label such fuses with labels of a non-heat resistant material, e.g. ordinary paper.
The situation is very different in high-voltage fuses, e.g. fuses having a voltage rating of 15 kv, and higher. In such fuses the length of the fuse tube results when the fuse is carrying current in a plateau-like zone of relatively high temperature between the ends of the fuse tube. The level of this plateau-like zone of relatively high temperature may be considerably higher than the peak temperatures found on the casings of relatively short low voltage fuses. As a result, high-voltage fuses cannot properly be labelled in the same fashion as low voltage fuses. As a general rule, the fuse tubes of high voltage fuses are imprinted with a heat resistant ink. This process is costly when it comes to processing large numbers of high-voltage fuses formed of many groups of which each group calls for an imprint of a different kind.
The present invention contemplates the use of labels of a non-temperature resistant material, e.g. paper, on high-voltage fuses.